A hobby loss is a financial loss that cannot be claimed as a business tax deduction, as it is the result of an activity that was not intended to earn a profit. The exact definition of “hobby loss” varies by jurisdiction. While the term is most commonly used in the United States, other countries may likewise have tax policies that restrict the ability to claim tax deductions on expenses for endeavors that are not true businesses. The hobby loss rule helps to prevent tax fraud by disallowing tax deductions for expenses that are not truly related to the operation of a for-profit business. If the activities of an individual aren’t considered to be those necessary to the operation of a legitimate business, the project can be classified by a taxing agency as a hobby, and expenses related to hobbies are often severely limited by tax codes. For example, in the United States, a hobby expense can be taken only as an itemized deduction.

在美国以及其他国家，经营企业的个人可以从他们的总收入中扣除经营企业的成本。 这些费用，如旅行、娱乐、维护办公室或其他设施的费用，可能是相当大的。 因此，企业主可以通过扣除这些费用来严格限制他或她的纳税义务。 政府税务机构，如国内税收署（IRS），意识到这些限制如何减少税收收入，因此制定了爱好损失政策，为税收目的界定合法商业活动的性质。

在企业主将各种费用和损失作为税收减免的情况下，税收征管机构可能会调查或审计纳税人的主张，运用爱好损失规则来确保减免是合法的。 在美国，税务审查员将调查有关企业及其所有者的细节，以确定该企业是真正的企业还是其所有者的爱好。 考虑因素包括所有者是否依赖企业的收入，以及任何损失是否是计划外事件的结果或在企业的初始阶段发生。 调查员还可能审查企业涵盖过去几年的财务记录。 如果企业在本次审计之前几年有盈利，调查员可能更倾向于将企业减免视为合法。